In recent years, electronic devices have undergone remarkable technical advances and integrated circuits having a higher density and higher performance have been rapidly developed. In response to such developments, printed wiring boards have come to have a higher density, more highly integrated wiring, and surface-mounted components. Such printed wiring boards also need to have a higher accuracy and higher performance than before. In response to such developments of integrated circuits having a higher density and higher performance, there have been studies on improvements in the performance of solder resist serving as a main material of integrated circuits. Build-up boards and the like having fine wiring therein still have a problem in that cracking occurs at the interface between solder resist and sealing resin, which is referred to as popcorning. Thus, there has been a demand for a solder resist having higher heat resistance.
With an increase in the degree of integration of integrated circuits, nanoimprint lithography has been attracting attention as a process for ultrafine patterning allowing a linewidth of 20 nm or less. This nanoimprint lithography is broadly divided into thermal nanoimprint lithography and photo nanoimprint lithography. The thermal nanoimprint lithography is performed in the following manner: a polymer resin is heated to a glass transition temperature or higher to be softened; a mold is pressed into this resin; and the mold is released from the resin having cooled, so that a fine structure is transferred to the resin on a substrate. Thus, nano-patterns can be formed at relatively low costs. The thermal nanoimprint lithography is expected to be applied in various fields. However, the thermal nanoimprint lithography requires softening of such a polymer resin by heating and polymer resins having a high glass transition temperature are difficult to use. Thus, the thermal nanoimprint lithography is difficult to apply to the electric and electronic field in which higher heat resistance has been required in recent years.
On the other hand, the photo nanoimprint lithography employs photo-curing of a composition upon irradiation with light. The photo nanoimprint lithography does not require heating of a molding material to which a pattern is transferred during pressing. Thus, imprinting can be achieved at room temperature. Photo-curable resins used for the photo nanoimprinting are of a radical polymerization type, an ionic polymerization type, and a hybrid of these types. Curable compositions of any of these types can be used for nanoimprinting. However, photo-curable compositions of the radical polymerization type, of which there is a wide choice of viable materials, have been commonly studied.
In the cases where materials for nanoimprinting are used for protective films and spacers for thin-film transistors and liquid crystal color filters in liquid crystal displays and for permanent films used for fine processing of other members for liquid crystal display apparatuses, cured products of the materials for nanoimprinting need to be excellent in terms of mechanical property, transparency, light resistance, heat resistance, or the like and, in particular, need to have very high heat resistance. Known examples of such a material that can provide cured products having high heat resistance are epoxy (meth)acrylate resins having a biphenyl skeleton (for example, refer to Patent Literature 1). However, these resins do not have the high heat resistance that has been required in recent years.